This invention relates to antenna element feed circuits, and in particular to exciters for energizing broadband, high impedance, slot antennas from lower impedance input transmission lines.
Apertured metallic ground plate type antenna elements (slot antennas, for instance) commonly have high input impedances. The input transmission lines that are used to feed these antenna elements have much lower impedances. A typical problem encountered by antenna designers is that of connecting an input 50 ohm line to excit an antenna element having a 200 ohm input impedance. The use of impedance matching devices and special circuits adds substantial cost and complexity to the antenna system. Furthermore, conventional approaches to the problem are often frequency dependent. The present invention is directed toward overcoming these problems through the use of a balanced exciter that effects both frequency independent impedance transformation and antenna element excitation.